# Vehicle steering wheel controls convertor with Arduino **URL:** \ **Category:** General Guidance\ **Created:** [October 8, 2024, 12:20am UTC](https://forum.arduino.cc/t/vehicle-steering-wheel-controls-convertor-with-arduino/1309038 "2024-10-08T00:20:53Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![outbackhut](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/outbackhut/32/1099892_2.png) [@outbackhut](https://forum.arduino.cc/u/outbackhut)\ **Post date:** [October 8, 2024, 12:20am UTC](https://forum.arduino.cc/t/vehicle-steering-wheel-controls-convertor-with-arduino/1309038/1 "2024-10-08T00:20:53Z")
I have a 2002 Astra Bertone convertible which has a six button steering wheel control. It worked with the original Blaupunkt 520 radio, however I have since replaced that with a touchscreen (Android Auto/ Car Play) HUD which is "compatible" with original steering wheel controls. All good so far. **BUT**. The steering wheel control lines are labelled GND, MRQ, SDA, and SCL, which makes me think that is I2C, and they are at a logic level of 5.01 volts (unsure what MRQ is, and nearly impossible to find info on Uncle Google). The HUD has GND, KEY1, and KEY2, which are for a resistance based steering wheel control. Should be fairly doable to use an arduino to convert between the two, however when I hook an arduino up to the GND, SDA, and SCL lines with I2C scanner code, it cannot find an address. Do I need to connect the 5v source between the two? Could the issue be different I2C speeds, and if so, how do I work out the vehicle I2C speed, having not been able to find documentation? How would you progress? Could it be some other communication protocol? Could it be the fact that I don't know what MRQ is (any ideas on what that could be - maybe a master request?)? ---
**Author:** ![outbackhut](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/outbackhut/32/1099892_2.png) [@outbackhut](https://forum.arduino.cc/u/outbackhut)\ **Post date:** [October 8, 2024, 1:54am UTC](https://forum.arduino.cc/t/vehicle-steering-wheel-controls-convertor-with-arduino/1309038/2 "2024-10-08T01:54:53Z")
Here is a link containing some possible related information: [http://forum.lcdinfo.com/viewtopic.php?f=6&t=2711](http://forum.lcdinfo.com/viewtopic.php?f=6&t=2711) So if that is correct, how do I know what lengths of time the signal needs to be high or low? ---
**Author:** ![gilshultz](https://avatars.discourse-cdn.com/v4/letter/g/67e7ee/32.png) [@gilshultz](https://forum.arduino.cc/u/gilshultz)\ **Post date:** [October 8, 2024, 3:03am UTC](https://forum.arduino.cc/t/vehicle-steering-wheel-controls-convertor-with-arduino/1309038/3 "2024-10-08T03:03:51Z")
What does this have to do with an Arduino? ---
**Author:** ![outbackhut](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/outbackhut/32/1099892_2.png) [@outbackhut](https://forum.arduino.cc/u/outbackhut)\ **Post date:** [October 8, 2024, 3:06am UTC](https://forum.arduino.cc/t/vehicle-steering-wheel-controls-convertor-with-arduino/1309038/4 "2024-10-08T03:06:17Z")
Wow, I'm dense. What I forgot to say is that I want to use an Arduino as a convertor between the two. > [@outbackhut](#): > > Should be fairly doable to use an arduino to convert between the two, however when I hook an arduino up to the GND, SDA, and SCL lines with I2C scanner code, it cannot find an address That wasn't clear. Does my Arduino have to somehow use MRQ as well as SDA and SCL? ---
**Author:** ![gilshultz](https://avatars.discourse-cdn.com/v4/letter/g/67e7ee/32.png) [@gilshultz](https://forum.arduino.cc/u/gilshultz)\ **Post date:** [October 8, 2024, 3:10am UTC](https://forum.arduino.cc/t/vehicle-steering-wheel-controls-convertor-with-arduino/1309038/5 "2024-10-08T03:10:37Z")
Can you post links to the technical information on the switches. It may also be in the radio schematic. I do not have time to check but here are two links you need to check: > **[BLAUPUNKT 520 HANDBOOK Pdf Download](https://www.manualslib.com/manual/537805/Blaupunkt-520.html)** > > View and Download Blaupunkt 520 handbook online. Audio System Handbook. 520 car stereo system pdf manual download. > **[Blaupunkt 520 Car Stereo System Manuals](https://www.manualslib.com/products/Blaupunkt-520-2972162.html)** > > Blaupunkt 520 Car Stereo System Pdf User Manuals. View online or download Blaupunkt 520 Car Stereo System Handbook, Operating And Installation Instructions ---
**Author:** ![outbackhut](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/outbackhut/32/1099892_2.png) [@outbackhut](https://forum.arduino.cc/u/outbackhut)\ **Post date:** [October 8, 2024, 3:21am UTC](https://forum.arduino.cc/t/vehicle-steering-wheel-controls-convertor-with-arduino/1309038/6 "2024-10-08T03:21:55Z")
> [@gilshultz](#): > > Can you post links to the technical information on the switches. I have scoured high and low for that, but cannot find it. I have the physical copy of that manual, it does not contain relevant information as to the communication protocol, or the wiring of those switches. There has to be some reverse engineering done, and I'm very bad at that. I'm guessing that the MRQ line is a high/low "enable" line. I might play around with that and see what happens. ---
**Author:** ![gilshultz](https://avatars.discourse-cdn.com/v4/letter/g/67e7ee/32.png) [@gilshultz](https://forum.arduino.cc/u/gilshultz)\ **Post date:** [October 8, 2024, 3:28am UTC](https://forum.arduino.cc/t/vehicle-steering-wheel-controls-convertor-with-arduino/1309038/7 "2024-10-08T03:28:21Z")
The key might lie in the radio schematic—you’ll need to determine what’s happening there. Resistor trees were commonly used in cars and were typically limited to about five buttons, which could be managed with just two or three wires. Keep in mind that ground may not necessarily be a separate wire. ---
**Author:** ![outbackhut](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/outbackhut/32/1099892_2.png) [@outbackhut](https://forum.arduino.cc/u/outbackhut)\ **Post date:** [October 8, 2024, 3:35am UTC](https://forum.arduino.cc/t/vehicle-steering-wheel-controls-convertor-with-arduino/1309038/8 "2024-10-08T03:35:35Z")
> [@gilshultz](#): > > Resistor trees were commonly used in cars and were typically limited to about five buttons There are six buttons, four wires with labels literally on them saying GND, MRQ, SDA, and SCL. I feel like that's not likely to be a resistor tree. Plus pressing the buttons does not change the output voltage, which I would think it would if the buttons had resistors on them? Though I don't know much about that, maybe the voltage isn't supposed to change from a resistor tree? I also thought about CAN bus, but why would the wires be labelled SDA and SCL? Maybe it is ICM2 rather than I2C ---
**Author:** ![outbackhut](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/outbackhut/32/1099892_2.png) [@outbackhut](https://forum.arduino.cc/u/outbackhut)\ **Post date:** [October 8, 2024, 3:41am UTC](https://forum.arduino.cc/t/vehicle-steering-wheel-controls-convertor-with-arduino/1309038/9 "2024-10-08T03:41:42Z")
> [@gilshultz](#): > > The key might lie in the radio schematic [blaupunkt\_420\_435\_520\_620\_635\_7648381510\_sch.pdf](https://forum.arduino.cc/uploads/short-url/iB3c4ZFGFJx31yiLUh4R3lkB5oY.pdf) (2.4 MB) You are a legend, a genius, amazing. The SDA and SCL on those wires aren't going to the steering control after all! ![Screenshot_20241008_143930_File Viewer](https://europe1.discourse-cdn.com/arduino/original/4X/f/3/9/f3961e4b153e863fad7cbb99ba8cda412dc8ea00.jpeg) Look at that! They go to the display!! But maybe what's worse is that there is now only ONE wire going to the steering wheel controls... Time to stick my DMM on that and see what it's doing!! Is it possible for a resistor tree to use only one output like that? ---
**Author:** ![GoForSmoke](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/goforsmoke/32/1127097_2.png) [@GoForSmoke](https://forum.arduino.cc/u/GoForSmoke)\ **Post date:** [October 8, 2024, 4:29am UTC](https://forum.arduino.cc/t/vehicle-steering-wheel-controls-convertor-with-arduino/1309038/10 "2024-10-08T04:29:48Z")
that wire and ground ---
**Author:** ![gilshultz](https://avatars.discourse-cdn.com/v4/letter/g/67e7ee/32.png) [@gilshultz](https://forum.arduino.cc/u/gilshultz)\ **Post date:** [October 8, 2024, 4:31pm UTC](https://forum.arduino.cc/t/vehicle-steering-wheel-controls-convertor-with-arduino/1309038/11 "2024-10-08T16:31:51Z")
> [@outbackhut](#): > > Is it possible for a resistor tree to use only one output like that? Yes, it will need either a power source or ground as the second wire, but only one wire would need to return. I expect the voltage will change as you press the buttons. If it’s not powered, try measuring the resistance (ohms) between the positive and negative terminals, as I’m unsure how it’s powered. ---
**Author:** ![system](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/system/32/1140315_2.png) [@system](https://forum.arduino.cc/u/system)\ **Post date:** [April 6, 2025, 4:31pm UTC](https://forum.arduino.cc/t/vehicle-steering-wheel-controls-convertor-with-arduino/1309038/12 "2025-04-06T16:31:53Z")
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